Strong sub-surface plastic deformation induced by high flux plasma in tungsten

We present experimental data obtained by post-examination of polycrystalline and single crystal tungsten exposed to high flux deuterium plasma (1024 D/m2/s). The exposures were performed in the temperature range 450-600 K and followed by nuclear reaction analysis (NRA), transmission electron microscopy (TEM) and nano-indentation measurements. Direct TEM observation of the high dislocation density in the sub-surface of the plasma-exposed samples implies the occurrence of strong (and fast) local plastic deformation apparently enhanced by the availability of deuterium penetrating in the material. The sharp NRA profile, as usually measured after high flux low temperature plasma exposure, correlates well with the dislocation density evolution and hardness increase within 10-15 μm of the material subsurface. Importantly, the heavy plastic deformation was induced in similar amounts in both commercial pure polycrystalline and single crystal tungsten grades.